A rights activist in Koh Kong province said Friday an investigation into the killing of environmental activist Chut Wutty in April had made some progress. But much of the case remains a mystery, said In Kong Chit, a rights investigator in the province for Licadho, who has met with all five witnesses of the April 26 shooting.

Chut Wutty and a military policemen were both shot dead in the incident. Witnesses have not been able to clarify what happened at the moment of the dual shooting, In Kong Chit said.

A special government committee concluded its own investigation shortly after the killing, claiming military policeman In Rattana was accidentally killed by a security guard for Timber Green, Rann Borath, after shooting Chut Wutty. That theory was met with skepticism by rights workers, however.

Min Makara, investigating judge for the Koh Kong provincial court, said the case against Rann Borath was moving, as witnesses are questioned over the incident.